There is a known type of video tape recorder in which video signals are converted into a digital signal (hereinafter referred to as a digital video signal) for recording and/or reproducing.
In particular, use of error correction techniques and the like with a digital video signal can prevent deterioration of picture quality even in case of repeated processing, such as repeated dubbing.
Incidentally in a video tape recorder of this type, it can be expected that if recording tracks can be formed more densely, then the total recording density would be proportionally enhanced.
However, with the tracking control techniques used in conventional video tape recorders, it has been difficult to perform tracking control with a high degree of accuracy. Therefore, if the recording track is to be formed with high density, there would be a problem in that adequate tracking control would not be assured.
Specifically, in a conventional tracking control technique, a control signal (CTL) is recorded on a control track formed in the longitudinal direction of the magnetic tape, and tracking control is carried out using this control signal (hereinafter referred to as the CTL method).
According to this CTL method, when recording is performed by the video tape recorder, the control track is formed in the longitudinal direction of the magnetic tape and the control signal is recorded on the control track with a signal level that varies in synchronicity with the rotation of the rotary drum. On the other hand, when reproduction is performed by the video tape recorder, a phase comparison is performed with respect to the control signal and a reference signal synchronized with the rotation of the rotary drum, and the phase of a capstan motor is controlled on the basis of the result of the phase comparison.
However, in magnetic tape recording devices, the distance between a position at which the control signal is recorded and a recording track formed diagonally on the magnetic tape can be subject to variation due to a variations in the tape tension at the time of recording or reproducing, changes in the magnetic tape with the passage of time, changes in the magnetic tape transport system, and so forth.
Accordingly, it is difficult to perform tracking control with a high degree of accuracy with the CTL method. If the recording track is formed with high density, then proper tracking would sometimes become impossible.
Meanwhile, there is another conventional method for tracking control in which a predetermined pilot signal to be used for tracking control is recorded on the recording track along with the video signals.
According to this method, a burst signal that is at a low frequency and thus is subject to a relatively low azimuth loss is selected as the pilot signal, and is recorded on the recording track at the time of recording the video signal.
On the other hand, at the time of reproduction, with this type of tracking control, the level of the pilot signal which leaks from adjacent tracks before and after the track being scanned is detected, and the capstan motor is phase-controlled to minimize the signal level.
However, with this method, when the recording or reproducing efficiency of the magnetic head varies for example, the minimum pilot signal level and the optimum scanning position of the magnetic head could diverge from optimum values. Therefore, if the recording track is formed with high density, this method also might fail to assure proper tracking control.
A further problem with this method is that upon repeated editing of the tape with insertion of material, the divergence in position would tend to accumulate so as to eventually cause disruption in the reproduced picture before and after the point of insertion.
In contrast, there is also another method in which the level of the reproduction signal obtained from the recording track is detected, and tracking control is executed to maximize the signal level.
In this method, however, the level of the reproduction signal varies with picture patterns, etc. thereby making it difficult to perform tracking control with a high degree of accuracy.
Further, with such a method, if the deviation from the proper track is by one track or more the use of azimuth recording would cause almost no reproduction signal to be detected, making it difficult to perform tracking control.
Even when the amount of deviation is less than one track, there is a disadvantage in that a certain amount of time is required to achieve proper tracking.